1977 K5 Blazer

Hey guys I just picked up a 1977 K5 blazer. I have a dew questions for everyone. Where is a good place to get parts for this truck. I need new fron seats, front fenders and doors. I am in Arizona. Is there anywhere here that sells parts for this??

I have some rust spots on this thing especially bellow the doors and on the bottom of the doors. Any good way of fixing this??? The doors will be easy to replace but bellow the door on the main body may be hard to do..